Phase change materials exhibit a large resistivity contrast between crystalline (low resistivity) and amorphous (high resistivity) phases. An electrical current passed through a phase change material can set or reset a phase change memory (PCM) device. To set a PCM device into the crystalline phase, a medium electrical current pulse can be used. To reset a PCM device into the amorphous phase, a large electrical current pulse for a short time period can be used. To read the state of a PCM device, a small electrical current is required. Accordingly, applications of phase change memory can be limited by the high current required to reset the PCM device.
Electrodes can be significant sources of heat loss away from the active region of the device. Heat loss outside the active region is wasted, and causes a demand for more current during the reset operation. Device density in the PCM memory array can be determined by the size of the memory cell access device, typically a diode or transistor. The size of the access device is decided in part by the peak reset current required to pass through the device. Therefore reducing reset current is desirable for scalability, high-density, and low power consumption in memory devices, including PCM and other programmable resistance memory types.